<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            /* 清除默认样式 */
           margin: 0;
           padding: 0;
           list-style: none;
           box-sizing: border-box;
        }
        div {
            height: 100px;
            width: 100px;
            background-color: pink;
            border: dashed 1px blue;
            padding: 20px;
            margin: 0 auto;
        }
    </style>
</head>
<body>
    <div>
        box
    </div>
</body>
</html>